1. Technical Field
The subject application relates to surgical stapling apparatus, and more particularly to a surgical staple and a drive member for driving a plurality of such staples from a cartridge assembly.
2. Background of Related Art
Surgical stapling apparatus are widely used in surgical procedures to fasten body tissue quickly and efficiently by driving fasteners or staples into the tissue. In certain types of staplers, a single staple is typically formed around an anvil, e.g., skin staplers, for approximating tissue. Such staplers may employ staples having a variety of configurations, as for example a conventional U-shaped configuration and variations thereon. See, e.g., U.S. Pat. No. 5,222,975 to Crainich.
In other types of staplers, such as those for mechanically stitching together hollow organs, the main linear drive, a cam member, moves longitudinally in a direction transverse to the direction the staples are to be driven. Typically, such staplers employ a number of staple drive members or pusher elements which pass through grooved slots of a staple retaining cartridge, such slots being arranged end-to-end in rows. Under normal operation, the longitudinally moving cam member passes into and through the cartridge, contacting cam surfaces on the drive members, thereby transversely pushing the drive members through the grooved slots. Thus, the drive members convert linear motion from the cam member to transverse staple motion. The rows of staples are thereby driven into the body tissue to be fastened.
An example of such an arrangement is described in commonly assigned U.S. Pat. No. 3,490,675 to Green et al. The drive member disclosed therein has a pusher plate, guide rails, and a V-shaped portion for contacting the driving cam. A further modification is illustrated in commonly assigned U.S. Pat. No. 3,499,591 to Green, which discloses a two staple driver capable of driving double rows of staples in a single cam stroke for greater holding strength than a single row. The two staple driver includes two drive sections in separate planes, with a v-shaped top surface for contacting the pusher cam. Each staple pair is staggered longitudinally (i.e., each staple is positioned diagonally behind the other, in a zig-zag fashion) and bridges the push-bar path. When the two staple drivers eject the pair of staples to engage tissue, the forces generated tend to be balanced in both the side-to-side and front-to-back directions, thereby decreasing any offset loading on the pushers.
U.S. Pat. No. 4,978,049 to Green discloses a staple drive member for applying three parallel rows of staples in a single ejection action and in staggered overlapping arrangement. The staple driver member disclosed therein comprises three pusher plates oriented in a staggered arrangement such that two outside plates are located predominantly at the proximal end, and one middle plate is located predominantly at the distal end. This configuration effectively balances the forces applied to the drive member when ejecting staples. Such a configuration also permits the application of a relatively smooth ejection force throughout the stapling operation. See also commonly assigned U.S. Pat. Nos. 5,040,715 and 4,978,049.
Each of the above-mentioned staple systems are commonly employed to drive conventional U-shaped staples having two opposed legs connected by a linear bridge. Therefore, the staple drivers have flat surfaces to correspond to the linear bridge portions of the staples. When deformed, such staples tend to form a B-shape, wherein the legs are curved towards the bridge and the chiseled end points are in a position to re-puncture the tissue being sutured. In such an orientation, a significant area of the deformed leg portions are not in extensive contact with the tissue. It would be desirable, therefore, to provide a staple which, when deformed, secures tissue along a greater length of the leg portions thereof and which does so with a reduced tendency to re-puncture the tissue being secured.